High pressure chromatography (HPLC) is a well-known chromatography mode wherein a pressurized liquid is used to force a sample through a chromatography column packed with a suitable particle media, known as the stationary phase. Flash chromatography differs from preparative HPLC in that larger particles are used to enable fast applications, typical particle sizes being in the broad range of 20-60 um. The Columns may be relatively simple tubes or syringes made from various materials, such as glass, quartz or stainless steel. Polymeric materials are becoming frequently used in pre-packed columns for construction of the columns or frits provided at each end to prevent the media from leaving.
Before running a chrothatographic separation, uniform conditions should be ensured throughout the packing of the column. This is usually provided by running a suitable mobile phase such as a solvent or a buffer through the column, which process is known as the equilibration or conditioning of a packed column. Since flash chromatography is primarily used for fast applications, the equilibration step is advantageously performed as quickly as possible, e.g. by utilizing few column volumes of mobile phase and/or high flow rates.
Grivel et al. (In J Chromatogr A 2010 Jan. 22; 1217(4):459-72: “Selection of suitable operating conditions to minimize the gradient equilibration time in the separation of drugs by Ultra-High-Pressure Liquid Chromatography with volatile (mass spectrometry-compatible) buffers) relates to reversed phase chromatography. More specifically, this article has recognized that problems are associated with long equilibraticm times in flash chromatography, and presents a study of temperature variation, different flow rates and various additives to the mobile phase used for equilibration. While drawing certain conclusions regarding retention variability and specific equilibration additives, it is also concluded by the authors that the mechanisms which govern equilibration remain very complex and require much further work.
U.S. Pat. No. 6,601,439 (“Method of reducing baseline instabilities in liquid chromatography measurements and liquid chromatography apparatus”) relates to high performance chromatography (HPLC) and problems associated by baseline variations, and specifically to instabilities in connection with amino functionalised stationary phases. The '439 patent describes how baseline variations originating from variations in the adsorption of water to the stationary phase have been found to be related to temperature fluctuations. According to this patent, the problems are reduced by the coupling of an additional solid body or liquid bath having high heat capacity and heat conductance to the column to enclose the equipment.